Describe the shape/structure of lymph nodes. Make a note of where concentrations of lymph nodes are found in the body. (2-3 paragraphs) Solution Lymph nodes are kidney or oval shaped and are few millimeters to about 1–2 cm long. Each lymph node is surrounded by a fibrous capsule,which is composed of dense irregular connective tissue with some plain collagenous fibers. From, the internal surface of the capsule, arise many maembranous processes called trabeculae. They pass inward, radiating toward the center of the node, for about one-third or one-fourth of the space between the circumference and the center of the lymph node. Inside the capsule, the lymph node is divided into the outer cortex and the inner medulla. The cortex is continuous around the medulla except where the medulla comes into direct contact with the hilum.Hilum is the depressed area of the surface of a lymph node through which the efferent lymphatics emerge from the medulla and through which blood vessels enter and leave the node. Actually, main function of the lymph nodes is the filtering of lymph to identify and fight infection. To do this, lymph nodes contains lymphocytes, a type of white blood cell, which includes B cells and T cells. The lymph node is divided into compartments called lymph nodules (or lobules) each consisting of a cortical region of combined follicle B cells, a paracortical region of T cells, and a basal part of the nodule in the medulla. Lymph is present throughout the body, and circulates through lymphatic vessels. These drain into and from lymph nodes -- afferent vessels drain into nodes, and efferent vessels from nodes. When lymph fluid enters a node, it drains into the node just beneath the capsule in a space called the subcapsular sinus. The subcapsular sinus drains into trabecular sinuses and finally into medullary sinuses. However, lymph nodes are most dense in the inguinal also called groin (lower portion of the anterior abdominal wall), axillary (where the arm connects the shoulder) and cervical regions of the body..